# File lib/ruport/data/table.rb, line 141
    def pivot(pivot_column, options = {})
      group_column = options[:group_by] || 
        raise(ArgumentError, ":group_by option required")
      value_column = options[:values]   || 
        raise(ArgumentError, ":values option required")
      Pivot.new(
        self, group_column, pivot_column, value_column, options
      ).to_table
    end